Flow control device

ABSTRACT

A flow control device for controlling the flow of refrigerant passing through an evaporator of a car cooler cycle or the like in which the difference between changes of the pressure and temperature of refrigerant at the outlet of the evaporator is converted into the displacement of a diaphragm in response to which the opening of an expansion valve is controlled, both of the static and dynamic pressures of refrigerant at the outlet of the evaporator are used as said pressure to actuate the diaphragm.

mted States Patent 1191 1111 3, Oshima et al. July 16, R973 FLOW CONTROL DEVICE [56] References Cited [76] lnventors:Yoiehiro Oshima, Seigo Miyamoto, UNITED STATES PATENTS Manabu Matumoto, all of Hitachi, 2,409,661 10/1946 Carter 62/225 Japan Primary ExaminerMeyer Perlin 1 Asslgneer HrtachpLtdy J p Attorney-Craig, Antonelli and Hill 22 Filed: Mar. 19,1971 [571 ABSTRACT A flow control device for controlling the flow of refrig- [21] PP N04 125,944 erant passing through an evaporator of a car cooler cycle or the like in which the difference between 0 Foreign Application priority Data changes of the pressure and temperature 0t: refrigerant Mar 23 l 970 Ja an 45/2358 at the outlet of the evaporator 1s converted mto the disp placement of a diaphragm in response to which the opening of an expansion valve is controlled, both of the (Cll. 6212;225:3632 static and dynamic pmssures of refrigerant at the Outlet [58] Field 210 212 of the evaporator are used as said pressure to actuate v 6 5 the diaphragm.

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ENG|NE 7 CONDENSER INVENTORS RYOICHRO OSHIMA SE\G0 MIYAMQTO w MANAa MATuMoTo BY Crawly, Anfonelli, jfeworbi ATTORNEYS FLOW CONTROL DEVICE BACKGROUND OF THE INVENTION The present invention relates to a flow control device for controlling the flow rate of refrigerant in a cycle of a car cooler or the like.

An expansion valve has been used in a typical prior art flow control device of the type described. In the prior art expansion valve, the temperature and pressure of refrigerant discharged out of an evaporator are detected and the deviations thereof from the reference values are applied to either sides of a diaphragm respectively so that the diaphragm displaces the valve in the expansion valve to control the opening of the passage of refrigerant to the evaporator. In general, the pressure representative of the temperature of refrigerant is acted upon one side of the diaphragm, while the pressure of refrigerant transmitted from the outlet of the evaporator through a pressure-equalizing or -balance line is acted upon .the other side. The temperature of refrigerant discharged from the evaporator is converted into the pressure by means of a heat sensing tube and is transmitted to a chamber at one side of the diaphragm through a capillary tube. However, when the cooler is started, or when the rapid change in outerside temperature occurs in case of the air conditioner, the load on the evaporator changes so that the evaporator cannot completely evaporate all of the refrigerant fed therein. Sometimes the liquid refrigerant is discharged out of the evaporator into the compressor, which is known as liquid-back phenomenon, and brings about the serious problem.

The prior art flow control device cannot quickly respond to the rapid pressure change of the refrigerant discharged out of the evaporator so that the flow of refrigerant cannot be suitably controlled to optimize the operation of the evaporator. As a consequence, the recovery of the refrigerant to the optimum superheated temperature is delayed so that the cooling capacity of refrigerant is much reduced. In addition, the operation of the evaporator is adversely affected and the noise problem is brought about because of the sudden increase in pressure in the evaporator.

In the prior art device, these problems are brought about because no special consideration have not been taken for detecting of the pressure of refrigerant discharged out of the evaporator. In other words, the prior art flow control device cannot detect the sudden change in pressure at the discharge port of the evaporator.

One of the objects of the present invention is therefore to provide an improved flow control device capable of quickly responding to the sudden pressure change at the outlet of an evaporator so as to optimize the flow rate of refrigerant to be fed into the evaporator, thereby overcoming the problems encountered in the prior art flow control device.

Another object of the present invention is to provide an improved flow control device which may be fabricated by a simple modification of the prior art flow control device.

SUMMARY OF THE INVENTION a pipe connected to the outlet of the evaporator so as to oppose the flow of discharged refrigerant so that both of the static and dynamic pressures of the discharged refrigerant may be acted upon one surface of the diaphragm in the flow control device.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic view ofa flow control device for coolers in accordance with the present invention; and

FIG. 2 is a view on enlarged scale of a portion A encircled by the dotted lines in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT An expansion valve 1 connected to an evaporator 2 has a valve 3 for controlling the flow to the evaporator 2. A casing 5 of the expansion valve 1 is divided into two chambers 7 and 8 by a diaphragm 6 and the first chamber 7 is in communication through a capillary tube 11 with a heat sensing tube 10 fixed to the outer wall of a line 9 from the outlet of the evaporator 2. The second chamber 8 is in communication through a pressure-equalizing or -balance line 12 with the line 9 and the opening end 12' of the pressure-equalizing line 12 is opposed to the flow of refrigerant as shown in FIG. 2. The flow of refrigerant is indicated by the arrow. As a consequence, both of the static and dynamic pressures are applied to the pressure-equalizing line 12. In FIG. 1, 13 denotes an adjustment spring; 14, a distributor of the evaporator; 15, a header; 16, a compressor driven by an engine 17; and 18, a condenser for exchanging heat carried by the refrigerant.

Next the mode of operation will be described. The expansion valve 1 controls the flow rate in response to the temperature and pressure of refrigerant passing through the line 9 from the evaporator. More specifically, when the temperature of the refrigerant is lowered or the pressure of refrigerant is increased, the diaphragm 6 deflects upwardly so that the valve 3 in the expansion valve 1 reduces the sectional area of the passage of the refrigerant. Consequently the feed of refrigerant to the evaporator is reduced. Thus in response to the variation in load the expansion valve 1 may control the flowrate of refrigerant to the evaporator.

However, when the compressor 16 is started the pressure in the second chamber 8 below the diaphragm 6 is suddenly reduced and there is some delay in temperature response from the heat sensing tube 10 so that the expansion valve 1 is wide-opened. However, theevaporator 2 cannot evaporate all of refrigerant. That is too much refrigerant is fed into the evaporator so that the liquid-back phenomenon occurs.

Furthermore, in case of an air conditioner for automobiles the liquid-back phenomenon also occurs when the door is opened because the low-temperature outside air reduces the capacity of the evaporator.

When the liquid-back phenomenon occurs in the car cooler or air conditioner, the static pressure in the line Q of the evaporator is increased. In addition, the dynamic pressure is also increased because of the presence of high-density liquid.

According to the present invention, the opening 12' of the pressure-equalizing line 12 is disposed so as to oppose the flow of refrigerant in the line 9, whereby 'the total pressure of refrigerant may be transmitted to the second chamber 8 below the diaphragm 6. As a consequence, the diaphragm 6 quickly responds not only to the static pressure but also to the dynamic pressure of refrigerantso that the valve 3 in the expansion valve 1 may be quickly displaced in response to the displacement of the diaphragm'6. As a consequence, in response to the occurrence of liquid-back phenomenon the opening of the expansion valve 1 may be immediately reduced so that the optimum quantity of refrigerant may be fed into the evaporator. Thus even when the liquid-back phenomenon occurs, it may be overcomed in its early stage, that is during the time the influence of the liquid-back phenomenon is relatively less.

Since the present invention may immediately overcome the liquid-back phenomenon, the refrigeration capacity of the cyclic system may be increased and the adverse influence upon the compressor may be eliminated.

There occurs no adverse effect even when the static and dynamic pressures of refrigerant are applied to the diaphragm 6 in the second chamber 8. The adjustment spring 13 may be selected mainly in view of the characteristics of the expansion valve under the normal condition and the suitable control characteristics may be attained for the normal and transient operations and for variation in load. it is understood that the present invention will not be limited to the fact that all dynamic pressure is applied to the diaphragm and that a partial dynamic pressure may be applied to the diaphragm depending upon its functional characteristics.

What is claimed is:

l. A heat exchanging cycle comprising a compressor driven by an engine, a condenser for removing heat carried by refrigerant, an evaporator for absorbing heat from environment by refrigerant flowing therethrough, an expansion valve disposed at the inlet of said evaporator for adiabatically expanding refrigerant, a diaphragm for controlling the opening of said expansion valve, characterized by means for transmitting a pressure corresponding to the temperature of the refrigerant at the outlet of said evaporator to a first chamber disposed at one side of said diaphragm, and means for transmitting both the static and dynamic pressures of the refrigerant at the outlet of said evaporator to a second chamber at the other side of said diaphragm.

2. A heat exchanging cycle as defined in claim 1, wherein the means for transmitting both the static and dynamic pressures of the refrigerant includes a pressure-equalizing pipe having the opening thereof disposed in a path of refrigerant from said evaporator so as to oppose the flow of refrigerant so that the static and dynamic pressures of refrigerant are applied to said second chamber.

3. A heat exchanging cycle comprising a compressor driven by an engine, a condenser for removing heat carried by a refrigerant, an evaporator forabsorbing heat from the environment by the refrigerant flowing therethrough, an expansion valve disposed at the inlet of said evaporator for adiabatically expanding the refrigerant, and a diaphragm for controlling the opening of said expansion valve, characterized in that first means responsive to the temperature of the refrigerant at the outlet of the evaporator provides a first control pressure corresponding to the temperature of the refrigerant to a first chamber disposed at one side of said diaphragm, and second means responsive to both the static and dynamic pressures of the refrigerant at the outlet of said evaporator provides a second control pressure including the static and dynamic pressures of the refrigerant to a second chamber disposed at the other side of said diaphragm.

4. A heat exchanging cycle as defined in claim 3, wherein said second means includes a pressureequalizing pipe having an opening disposed in a path of the refrigerant so as to oppose the flow of the refrigerant from said evaporator. 

1. A heat exchanging cycle comprising a compressor driven by an engine, a condenser for removing heat carried by refrigerant, an evaporator for absorbing heat from environment by refrigerant flowing therethrough, an expansion valve disposed at the inlet of said evaporator for adiabatically expanding refrigerant, a diaphragm for controlling the opening of said expansion valve, characterized by means for transmitting a pressure corresponding to the temperature of the refrigerant at the outlet of said evaporator to a first chamber disposed at one side of said diaphragm, and means for transmitting both the static and dynamic pressures of the refrigerant at the outlet of said evaporator to a second chamber at the other side of said diaphragm.
 2. A heat exchanging cycle as defined in claim 1, wherein the means for transmitting both the static and dynamic pressures of the refrigerant includes a pressure-equalizing pipe having the opening thereof disposed in a path of refrigerant from said evaporator so as to oppose the flow of refrigerant so that the static and dynamic pressures of refrigerant are applied to said second chamber.
 3. A heat exchanging cycle comprising a compressor driven by an engine, a condenser for removing heat carried by a refrigerant, an evaporator for absorbing heat from the environment by the refrigerant flowing therethrough, an expansion valve disposed at the inlet of said evaporator for adiabatically expanding the refrigerant, and a diaphragm for controlling the opening of said expansion valve, characterized in that first means responsive to the temperature of the refrigerant at the outlet of the evaporator provides a first control pressure corresponding to the temperature of the refrigerant to a first chamber disposed at one side of said diaphragm, and second means responsive to both the static and dynamic pressures of the refrigerant at the outlet of said evaporator provides a second control pressure including the static and dynamic pressures of the refrigerant to a second chamber disposed at the other side of said diaphragm.
 4. A heat exchanging cycle as defined in claim 3, wherein said second means includes a pressure-equalizing pipe having an opening disposed in a path of the refrigerant so as to oppose the flow of the refrigerant from said evaporator. 